// Vertex Shader

void main()
{
    vec3 normal = normalize(gl_NormalMatrix * gl_Normal);
    vec3 lightDir = normalize(vec3(gl_LightSource[0].position));
    float NdotL = max(dot(-normal, lightDir), 0.0);
    vec4 diffuse = gl_FrontMaterial.diffuse *
                   gl_LightSource[0].diffuse;
    gl_FrontColor =  NdotL * diffuse;
    gl_Position = ftransform();
}